Mixed disulfides

ABSTRACT

This invention is directed to compounds of the formula ##STR1## wherein A and A 1  are amino acid residues, X is an α-imino acid residue, and R 1  is hydrogen, lower alkyl, or halo substituted lower alkyl. These compounds are useful as hypotensive agents.

This is a division, of application Ser. No. 146,729, filed May 2, 1980,now U.S. Pat. No. 4,284,624.

BACKGROUND OF THE INVENTION

Ondetti et al. in U.S. Pat. No. 4,105,776 disclose various mercaptoacyl,acylmercaptoacyl, substituted mercaptoacyl, and disulfideacylN-substituted prolines. The proline ring can be substituted, forexample, in the 4-position by a hydroxy or lower alkyl group. Ondetti etal. disclose that these compounds are useful as hypotensive agents dueto their angiotensin converting enzyme inhibitory activity. Among thecompounds disclosed by Ondetti et al. is captopril,1-(D-3-mercapto-2-methylpropanoyl)-L-proline.

Wong et al., "The In Vitro Metabolism of ¹⁴ C-Captopril In The Blood ofRats, Dogs and Humans", Pharmacologist, Vol. 21, p. 173 (August, 1979)identifies captopril-glutathione and captopril-cysteine mixed disulfidesas metabolites of captopril.

Ondetti et al. in U.S. Pat. No. 4,154,935 disclose that variousmercaptoacyl 4-halo or 4,4-halo substituted prolines and thecorresponding disulfides are useful hypotensive agents.

Ondetti in U.S. Pat. No. 4,192,878 disclose that various mercaptoacylthiazolidinecarboxylic acids are useful hypotensive agents.

Ondetti et al. in U.S. Pat. No. 4,154,942 discloses that variousmercaptoacyl 3,4-dehydroprolines and the corresponding disulfides areuseful hypotensive agents.

SUMMARY OF THE INVENTION

This invention is directed to new mixed disulfides of formula I andsalts thereof ##STR2##

A and A₁ each is an amino acid residue. The amino acid represented by Ais joined through a carbonyl group, ##STR3## while the amino acidrepresented by A₁ is joined through an amino group, --NH--. A and A₁ arepreferably selected from glycyl, alanyl, valyl, leucyl, α- orγ-glutamyl, α- or β-aspartyl, phenylalanyl, tyrosyl, tryptophyl, lysyl,arginyl, or prolyl.

X is a naturally occurring or synthetic α-imino acid residue joinedthrough its N-atom. Exemplary α-imino acid residues are groups of theformulas: ##STR4##

R₁ is hydrogen, lower alkyl, or halo substituted lower alkyl.

R₂ is hydrogen, hydroxy, lower alkyl, halogen, keto, ##STR5##

Y is O or S.

R₅ is lower alkyl, substituted or unsubstituted phenyl, substituted orunsubstituted phenyl-lower alkylene, substituted or unsubstituted 1- or2-naphthyl, or substituted or unsubstituted biphenyl.

R₆ is halogen or --Y--R₇.

R₇ is lower alkyl, substituted or unsubstituted phenyl, substituted orunsubstituted phenyl-lower alkylene, or the R₇ groups join to completean unsubstituted 5- or 6-membered ring or said ring in which one or moreof the carbon atoms has a lower alkyl or di(lower alkyl) substituent.

R₃, R₄, R₈ and R₉ are independently selected from hydrogen and loweralkyl.

DETAILED DESCRIPTION OF THE INVENTION

This invention in its broadest aspect relates to the mixed disulfides offormula I above and to salts thereof, to compositions containing suchcompounds and to the method of using such compounds as anti-hypertensiveagents.

The term lower alkyl used in the definition of the various symbols arestraight or branched chain hydrocarbon radicals having up to four carbonatoms, i.e., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl.Methyl and ethyl are the preferred lower alkyl groups. Similarly, theterms lower alkoxy and lower alkylthio refer to such groups attached toan oxygen or sulfur.

The term halogen refers to chloro, bromo and fluoro and the term halosubstituted lower alkyl refers to such lower alkyl groups describedabove in which one or more hydrogens have been replaced by chloro, bromoor fluoro groups such as trifluoromethyl, pentafluoroethyl,2,2,2-trichloroethyl, chloromethyl, bromomethyl, etc.

The term phenyl-lower alkylene refers to groups of the formula ##STR6##wherein m is an integer from 1 to 4. Preferred phenyl-lower alkylenegroups are phenylmethyl and phenylethyl, especially phenylmethyl.

The terms substituted phenyl, substituted phenyl-lower alkylene,substituted 1- or 2-naphthyl, and substituted biphenyl include suchgroups having one or two, preferably one, substituent on the ring.Suitable substituents include lower alkyl groups of 1 to 4 carbons,especially methyl, lower alkoxy groups of 1 to 4 carbons, especiallymethoxy, lower alkylthio groups of 1 to 4 carbons, especiallymethylthio, halogens, especially chloro or fluoro, trifluoromethyl,acetyloxy and hydroxy. The hydroxy substituted compounds are obtained byhydrolysis of the corresponding acetyloxy substituted compound as thelast step of the synthetic procedure.

Preferred compounds of this invention are those wherein R₁ is hydrogen,methyl or trifluoromethyl, especially methyl; A is γ-glutamyl; A₁ isglycyl; and X is (L)-proline, 4-hydroxy-(L)-proline,4-methoxy-(L)-proline, 4,4-ethylenedioxo-(L)-proline,4,4-ethylene-dithio-(L)-proline, 4-phenoxy-(L)-proline,4-phenylthio-(L)-proline, 4-(2-naphthenyloxy)-(L)-proline,4-([1,1-biphenyl]-4-yloxy)-(L)-proline, or (L)-thiazolidine-4-carboxylicacid, especially (L)-proline.

When R₁ is methyl or trifluoromethyl the asymmetric carbon to which R₁is attached is preferably in the D-configuration. The asymmetric carbonto which ##STR7## and A--NH-- are attached is preferably in theL-configuration as are any other asymmetric carbons that may be presentin the A and A₁ groups.

The compounds of formula I are obtained by reacting the3-sulfenylphthalimido compound of the formula ##STR8## wherein Z is thebenzhydryl ester of the α-imino acid residue X, with the tripeptide##STR9## followed by treatment with trifluoroacetic acid, acetic acid,and anisole to remove the benzhydryl group. The tripeptides of formulaIII are prepared by procedures known in the art of peptide synthesis.See for example Methoden der Organischen Chemie(Houben Wieyl) Vol. XV,parts 1 and 2 (1974).

The 3-sulfenylphthalimido intermediate of formula II is obtained bytreating the disulfide ##STR10## with diphenyldiazomethane to yield theester product ##STR11## which is then reacted in an organic solvent withbromine and potassium phthalimide.

The disulfide of formula IV is obtained by directly oxidizing withiodine the mercaptoacyl compound of the formula ##STR12## Themercaptoacyl compounds of formula VI are obtained by coupling theα-imino acid, HX, with an acid or its chemical equivalent of the formula##STR13## wherein R₁₀ is a hydrolyzably or chemically removableprotecting group.

The disulfides of formula IV are disclosed in various patents andpending applications depending upon the definition of X. For example,those compounds wherein X is proline, 4-lower alkyl proline, or4-hydroxyproline are disclosed by Ondetti et al. in U.S. Pat. No.4,105,776, those compounds wherein X is mono or dihalo substitutedproline are disclosed by Ondetti et al. in U.S. Pat. No. 4,154,935,those wherein X is carbamoyloxy substituted proline are disclosed byKrapcho in U.S. Ser. No. 66,119, now U.S. Pat. No. 4,217,359, thosewherein X is an ether or thioether 4-substituted proline are disclosedby Ondetti et al. in U.S. Ser. No. 126,239, those wherein X is a 4-ketosubstituted proline are disclosed by Ondetti in U.S. Ser. No. 112,004,now U.S. Pat. No. 4,296,113, those wherein X is an ether or thioether4,4-substituted proline are disclosed by Krapcho in U.S. Ser. No.99,164, those wherein X is a thiazolidine carboxylic acid are disclosedby Ondetti in U.S. Pat. No. 4,192,878, those wherein X is a 5-ketosubstituted proline by Ondetti et al. in U.S. Ser. No. 51,772, now U.S.Pat. No. 4,234,489, and those wherein X is a 3,4-dehydroproline aredisclosed by Ondetti et al. in U.S. Pat. No. 4,154,942.

The compounds of this invention being amphoteric in nature form basicand acid addition salts with a variety of inorganic or organic bases andacids. The salt forming ion derived from such bases can be metal ions,e.g., aluminum, alkali metal ions, such as sodium or potassium, alkalineearth metal ions such as calcium or magnesium, or an amine salt ion, ofwhich a number are known for this purpose, for example aralkylamineslike, dibenzylamine, N,N-dibenzylethylenediamine, lower alkylamines likemethylamine, t-butylamine, procaine, lower alkylpiperidines likeN-ethylpiperidine, cycloalkylamines, like cyclohexylamine ordicyclohexylamine, 1-adamantanamine, benzathine, or salts derived fromamino acids like arginine, lysine or the like. The physiologicallyacceptable salts like the sodium or potassium salts can be usedmedicinally as described below and are preferred. The acid additionsalts are derived from inorganic acids such as hydrochloric or sulfuricor organic acids such as acetic, malic, maleic, succinic, tartaric, etc.

The compounds of formula I and their physiologically acceptable saltsare useful as hypotensive agents. They inhibit the conversion of thedecapeptide angiotensin I to angiotensin II and, therefore, are usefulin relieving angiotensin related hypertension. The action of the enzymerenin on angiotensinogen, a pseudo-globulin in blood plasma, producesangiotensin I. Angiotensin I is converted by angiotensin convertingenzyme (ACE) to angiotensin II. The latter is an active pressorsubstance which has been implicated as the causative agent in variousforms of hypertension in various mammalian species, e.g., rats and dogs.The compounds of this invention intervene in theangiotensin→(renin)→angiotensin I→(ACE)→angiotensin II sequence byinhibiting angiotensin converting enzyme and reducing or eliminating theformation of the pressor substance angiotensin II. Thus by theadministration of a composition containing one, or a combination ofcompounds of formula I, angiotensin dependent hypertension in thespecies of mammal suffering therefrom is alleviated. A single dose, orpreferably two to four divided daily doses, provided on a basis of about0.1 to 100 mg. per kilogram of body weight per day, preferably about 1to 15 mg. per kilogram of body weight per day is appropriate to reduceblood pressure. The substance is preferably administered orally, butparenteral routes such as the subcutaneous, intramuscular, intravenousor intraperitoneal routes can also be employed.

The compounds of this invention can also be formulated in combinationwith a diuretic for the treatment of hypertension. A combination productcomprising a compound of this invention and a diuretic can beadministered in an effective amount which comprises (for a 70 kg.mammal) a total daily dosage of about 30 to 600 mg., preferably about 30to 300 mg., of a compound of this invention, and about 15 to 300 mg.,preferably about 15 to 200 mg. of the diuretic, to a mammalian speciesin need thereof. Exemplary of the diuretics contemplated for use incombination with a compound of this invention are the thiazidediuretics, e.g., chlorthiazide, hydrochlorothiazide, flumethiazide,hydroglumethiazide, bendroflumethiazide, methchlothiazide,trichlormethiazide, polythiazide or benzthiazide, as well as ethacrynicacid, ticrynafen, chlorthalidone, furosemide, musolimine, bumetanide,triamterene, amiloride and spironolactone, and PG,13 salts of suchcompounds.

The compounds of formula I can be formulated for use in the reduction ofblood pressure in compositions such as tablets, capsules or elixirs fororal administration or in sterile solutions or suspensions forparenteral administration. About 10 to 500 mg. of a compound or mixtureof compounds of formula I is compounded with a physiologicallyacceptable vehicle, carrier, excipient, binder, preservative,stabilizer, flavor, etc., in a unit dosage form as called for byaccepted pharmaceutical practice. The amount of active substance inthese compositions or preparations is such that a suitable dosage in therange indicated is obtained.

Illustrative process details are set forth in the following examples forthe various reactions. These examples are preferred embodiments and alsoserve as models for the preparation of other compounds of thisinvention. The temperatures are given in degrees on the centigradescale.

EXAMPLE 1(S,S)-N-[3-[[3-(2-Carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine(a) 1,1'-[Dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)]bis[L-proline]

3 g. of 1-(3-mercapto-2-D-methylpropanoyl)-L-proline, prepared forexample according to the procedure of Example 34 in U.S. Pat. No.4,105,776, is dissolved in 67 ml. of water and the pH is adjusted to 6.5with N sodium hydroxide. To this a total of 27.8 ml. of 0.5 M iodinesolution (95% ethanol) is added dropwise while maintaining a pH of 5.5to 6.5 with N sodium hydroxide. After fifteen minutes a trace of excessiodine is discharged with dilute sodium thiosulfate. The reactionmixture is concentrated in vacuo, acidified with concentrated HCl andthe crystals filtered to yield 2.77 g. of1,1'-[dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)]bis[L-proline]; m.p.235°-237°. Recrystallization from methanol yields 1.52 g. of pure1,1'-[dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)bis[L-proline]; m.p.236°-237°.

(b) 1,1'-[Dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)]bis[L-proline],dibenzhydryl ester

Diphenyldiazomethane (20.8 g., 107 mmol.) is added to methanolicsolution (250 ml.) containing 12 g. (27.8 mmol.) of1,1'-[dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)]bis[L-proline]. Thesolution is stirred at room temperature overnight. The separated solidis filtered and dried to yield 18.7 g. of1,1'-[dithiobis(D-2-methyl-1-oxopropane-3,1-diyl)]bis[L-proline],dibenzhydryl ester; m.p. 149°-152°; [α]_(D) ²⁵ =-188° (c=2, chloroform).

(c) 1-[3-Sulfenylphthalimido-2-D-methylpropanoyl]-L-proline, benzhydrylester

Bromine (3.2 g., 20 mmol.) in 6 ml. of dichloroethane is added to anice-cold solution of the dibenzhydryl ester product from part (b) (4.96g., 6.5 mmol.) in 24 ml. of dichloroethane. The solution is stirred forthree minutes and 4.96 g. (27 mmol.) of potassium phthalimide is addedalong with another 30 ml. of dichloroethane. After stirring in theice-bath for fifteen minutes, the solution is stirred for 2.5 hours atroom temperature. The solution is then centrifuged and the clear orangesolution is evaporated and reevaporated from dichloroethane. The residueis dissolved in ethanol and concentrated to yield 5.2 g. of whitecrystalline 1-[3-sulfenylphthalimido-2-D-methylpropanoyl]-L-proline,benzhydryl ester; m.p. 142°-146° (dec. 141°); [α]_(D) ²⁵ =95° (c=1,chloroform).

(d)(S,S)-N-[3-[[3-(2-Carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine

A mixture of glutathione (2.37 g., 7.7 mmole.) and1-[3-sulfenylphthalimido-2-D-methylpropanoyl]-L-proline, benzhydrylester (4.5 g., 8.5 mmol.) in 100 ml. of ethanol are refluxed for threehours. The solution is left overnight at room temperature. The separatedsolid is filtered off (4.4 g.) and the mother liquor evaporated (2.2g.). Since both contain the desired product, they are deprotectedseparately using a mixture of trifluoroacetic acid (5 ml.), acetic acid(4 ml.), and anisole (1 ml.). The deprotected product from the tworeactions (3.3 g. and 0.9 g.) are combined along with a 1.1 g. samplefrom an earlier small scale experiment. The total combined deprotectedmaterial (5.3 g.) is applied on a column of silica gel (mesh 60-200)built in n-butanol-acetic acid-water (4:1:1). The column is eluted withthe same solvent system using gravity and the separation is repeatedunder moderate pressure for a fast column in the same system (silicagel, mesh 230-400). The fractions containing the desired product arepooled, evaporated, and the water soluble portion of this material isapplied on a LH-20 column (2.5 cm×110 cm.) built in water and elutedwith water. 10 ml. fractions are collected and fractions 40-51containing the desired product as a homogeneous material are pooled andlyophilized to yield 0.95 g. of (S,S)-N-[3-[[3-(2-carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine;[α]_(D) ²⁵ =-175° (c=1, water); R_(f) =0.2, n-butanol: acetic acid:water(4:1:1) on electrophoresis (2000 V, 25 minutes) in the pyridine-acetatepH 6.5 buffer it had a 130% mobility as that of aspartic acid.

Anal. Calc'd. for C₁₉ H₃₀ N₄ S₂ : C, 43.67; H, 5.79; N, 10.72; S, 12.27.C₁₉ H₃₀ N₄ S₂.4H₂ O: C, 38.38; H, 6.44; N, 9.42; S, 10.78. Found: C,38.44; H, 5.20; N, 9.59; S, 9.82.

EXAMPLES 2-35

Following the procedure of Example 1 but employing the α-imino acid ofCol. I one obtains the product listed in Col. II.

    __________________________________________________________________________    Example                                                                              Col. I        Col. II                                                  __________________________________________________________________________    2      1-(3-mercaptopropanoyl)-                                                                    (S)-N-[3-[[3-(2-carboxy-1-                                      L-proline     pyrrolidinyl)-3-oxopropyl]-                                                   dithio]-N-(L-γ-glutamyl)-L-                                             alanyl]glycine                                           3      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-                                    methylpropanoyl)-4-                                                                         hydroxy-1-pyrrolidinyl)-2-methyl-                               hydroxy-L-proline                                                                           3-oxopropyl]dithio]-N-(L-γ-glutamyl)-                                   L-alanyl]glycine                                         4      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-1-pyrro-                              trifluoromethyl-                                                                            lidinyl)-2-trifluoromethyl-3-oxo-                               propanoyl)-L-proline                                                                        propyl]dithio]-N-(L-γ-glutamyl)-                                        L-alanyl]glycine                                         5      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-methyl-                             methylpropanoly)-4-                                                                         1-pyrrolidinyl)-2-methyl-3-oxopropyl]-                          methyl-L-proline                                                                            dithio]-N-(L-γ-glutamyl)-L-alanyl]-                                     glycine                                                  6      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-chloro-                             methylpropanoyl)-4-                                                                         1-pyrrolidinyl)-2-methyl-3-oxo-                                 chloro-L-proline                                                                            propyl]dithio]-N-(L-γ-glutamyl)-L-                                      alanyl]glycine                                           7      1-(3-mercaptopropan-                                                                        (S)-N-[3-[[3(2-carboxy-4-fluoro-                                oyl)-4-fluoro-L-proline                                                                     1-pyrrolidinyl)-3-oxopropyl]di-                                               thio]-N-(L-γ-glutamyl)-L-alanyl]-                                       glycine                                                  8      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-                                    methylpropanoyl)-4-                                                                         phenoxy-1-pyrrolidinyl)-2-methyl-                               phenoxy-L-proline                                                                           3-oxopropyl]dithio]-N-(L-γ-glu-                                         tamyl)-L-alanyl]glycine                                  9      1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-                                    methylpropanoyl)-4-                                                                         phenylthio-1-pyrrolidinyl)-2-                                   phenylthio-L-proline                                                                        methyl-3-oxopropyl]dithio]-N-                                                 (L-γ-glutamyl)-L-alanyl]glycine                    10     1-(3-mercapto-2-D-tri-                                                                      (S,S)-N-[3-[[3-[2-carboxy-4-                                    fluoromethylpropanoyl)-                                                                     [[(4-methyl)phenyl]oxy]-1-                                      4-[[(4-methyl)phenyl]-                                                                      pyrrolidinyl]-2-trifluoromethyl-                                oxy]-L-proline                                                                              3-oxopropyl]dithio]-N-(L-γ-glu-                                         tamyl)-L-alanyl]  glycine                                11     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-                                    methylpropanoyl)-4-                                                                         methoxy-1-pyrrolidinyl)-2-methyl-                               methoxy-L-proline                                                                           3-oxopropyl]dithio]-N-(L-γ-glu-                                         tamyl)-L-alanyl]glycine                                  12     1-(3-mercaptopropanoyl)-                                                                    (S)-N-[3-[[(2-carboxy-4-                                        4-ethoxy-L-proline                                                                          ethoxy-1-pyrrolidinyl)-3-                                                     oxopropyl]dithio]-N-(L-γ-                                               glutamyl)-L-alanyl]glycine                               13     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-[2-carboxy-4-                                    methylpropanoyl)-4-                                                                         (1,1-dimethylethoxy)-1-pyrroli-                                 (1,1-dimethylethoxy)-                                                                       dinyl]-2-methyl-3-oxopropyl]di-                                 L-proline     thio]-N-(L-γ-glutamyl)-L-alanyl]-                                       glycine                                                  14     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4-                                    methylpropanoyl)-4-                                                                         methylthio-1-pyrrolidinyl)-2-                                   methylthio-L-proline                                                                        methyl-3-oxopropyl]dithio]-N-                                                 (L-γ-glutamyl)-L-alanyl]glycine                    15     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[ [3-[2-carboxy-4-                                   methylpropanoyl)-4-                                                                         ([1,1'-biphenyl]-4-yloxy)-1-                                    ([1,1'-biphenyl]-4-                                                                         pyrrolidinyl]-2-methyl-3-oxo-                                   yloxy)-L-proline                                                                            propyl]dithio]-N-(L-γ-glutamyl)-                                        L-alanyl]glycine                                         16     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-[2-carboxy-4-                                    methylpropanoyl)-4-                                                                         (2-naphthalenyloxy)-1-pyrroli-                                  (2-naphthylenyloxy)-L-                                                                      dinyl]-2-methyl-3-oxopropyl]di-                                 proline       thio]-N-(L-γ-glutamyl)-L-alanyl]-                                       glycine                                                  17     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-                                      methylpropanoyl)-4-                                                                         4-keto-1-pyrrolidinyl)-2-                                       keto-L-proline                                                                              methyl-3-oxopropyl]dithio]-                                                   N-(L-γ-glutamyl)-L-alanyl]-                                             glycine                                                  18     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-[2-carboxy-                                      methylpropanoyl)-4-                                                                         4-[[(methylamino)carbonyl]-                                     [[(methylamino)car-                                                                         oxy]-1-pyrrolidinyl]-2-methyl-                                  bonyl]oxy]-L-proline                                                                        3-oxopropyl]dithio]-N-                                                        (L-γ-glutamyl)-L-alanyl]-                                               glycine                                                  19     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[ 3-(2-carboxy-4,4-                                 trifluoromethylpro-                                                                         dichloro-1-pyrrolidinyl)-2-                                     panoyl)-4,4-dichloro-                                                                       trifluoromethyl-3-oxopropyl]-                                   L-proline     dithio]-N-(L-γ-glutamyl)-L-alanyl]-                                     glycine                                                  20     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4,4-                                  methylpropanoyl)-4,4-                                                                       difluoro-1-pyrrolidinyl)-2-                                     difluoro-L-proline                                                                          methyl-3-oxopropyl]dithio]-N-                                                 (L-γ-glutamyl)-L-alanyl]glycine                    21     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-                                      methylpropanoyl)-4,4-                                                                       4,4-dimethoxy-1-pyrrolidinyl)-                                  dimethoxy-L-proline                                                                         2-methyl-3-oxopropyl]dithio]-                                                 N-(L-γ-glutamyl)-L-alanyl]-                                             glycine                                                  22     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4,4-                                  methylpropanoyl)-4,4-                                                                       dimethylthio-1-pyrrolidinyl)-2-                                 dimethylthio-L-proline                                                                      methyl-3-oxopropyl]dithio]-N-                                                 (L-γ-glutamyl)-L-alanyl]glycine                    23     1-(3-mercaptopro-                                                                           (S)-N-[3-[[3-(2-carboxy-4,4-                                    panoyl)-4,4-diethoxy-                                                                       diethoxy-1-pyrrolidinyl)-3-                                     L-proline     oxopropyl]dithio]-N-[L-γ-                                               glutamyl)-L-alanyl]glycine                               24     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-                                      methylpropanoyl)-4,                                                                         4,4-ethylenedioxy-1-pyrrolidinyl)-                              4-ethylenedioxy-L-pro-                                                                      2-methyl-3-oxopropyl]dithio]-                                   line          N-(L-γ-glutamyl)-L-alanyl]-                                             glycine                                                  25     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4,4-                                  methylpropanoyl)-4,                                                                         ethylenedithio-1-pyrrolidinyl)-2-                               4-ethylenedithio-L-                                                                         methyl-3-oxopropyl]dithio]-N-                                   proline       (L-γ-glutamyl)-L-alanyl]glycine                    26     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-4,                                    methylpropanoyl)-4,                                                                         4-trimethylenedioxy-1-pyrroli-                                  4-trimethylenedioxy-                                                                        dinyl)-2-methyl-3-oxopropyl]-                                   L-proline     dithio]-N-(L-γ-glutamyl)-L-                                             alanyl]glycine                                           27     1-(3-mercapto-2-D-                                                                          (S,S-N-[3-[[3-(2-carboxy-4,4-                                   trifluoromethylpro-                                                                         ethylenedioxy-1-pyrrolidinyl)-                                  panoyl)-4,4-ethylene-                                                                       2-trifluoromethyl-3-oxopropyl]-                                 dioxy-L-proline                                                                             dithio] -N-(L-γ-glutamyl)-L-alanyl]                                     glycine                                                  28     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-[2-carboxy-4,4-                                  methylpropanoyl)-4,                                                                         (1-methylethylenedioxy)-1-                                      4-(1-methylethylene-                                                                        pyrrolidinyl]-2-methyl-3-oxo-                                   dioxy-L-proline                                                                             propyl]dithio]-N-(L-γ-glutamyl)-                                        L-alanyl]glycine                                         29     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-[2-carboxy-                                      methylpropanoyl)-4,                                                                         4,4-(phenylmethoxy)-1-                                          4-(phenylmethoxy)-                                                                          pyrrolidinyl]-2-methyl-3-                                       L-proline     oxopropyl]dithio]-N-(L-γ-                                               glutamyl)-L-alanyl]glycine                               30     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[-(2-carboxy-                                       methylpropanoyl)-5-                                                                         5-keto-1-pyrrolidinyl)-2-                                       keto-L-proline                                                                              methyl-3-oxopropyl]dithio]-                                                   N-(L-γ-glutamyl)-L-alanyl]glycine                  31     1-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-                                      methylpropanoyl)-L-                                                                         2,5-dihydro-1H-pyrrol-1-yl)-2-                                  3,4-dehydroproline                                                                          methyl-3-oxopropyl]dithio]-                                                   N-(L-γ-glutamyl)-L-alanyl]glycine                  32     3-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(4-carboxy-                                      methylpropanoyl)-4-                                                                         3-thiazolidinyl)-2-methyl-3-                                    L-thiazolidinecar-                                                                          oxopropyl]dithio]-N-(L-γ-                                 boxylic acid  glutamyl)-L-alanyl]glycine                               33     3-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(4-carboxy-3-                                    2-trifluoromethyl-                                                                          thiazolidinyl)-2-trifluoromethyl-                               propanoyl)-4-L-thia-                                                                        3-oxopropyl]dithio]-N-(L-γ-                               zolidinecarboxylic                                                                          glutamyl)-L-alanyl]glycine                                      acid                                                                   34     3-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(2-carboxy-3-                                    methylpropanoyl)-2-                                                                         thiazolidinyl)-2-methyl-3-                                      L-thiazolidinecar-                                                                          oxopropyl]dithio]-N-(L-γ-                                 boxylic acid  glutamyl)-L-alanyl]glycine                               35     3-(3-mercapto-2-D-                                                                          (S,S)-N-[3-[[3-(4-carboxy-                                      methylpropanoyl)-2,2-                                                                       2,2-dimethyl-3-thiazolidinyl)-                                  dimethyl-4-L-thiazoli-                                                                      2-methyl-3-oxopropyl]dithio]-                                   diencarboxylic acid                                                                         N-(L-γ-glutamyl)-L-alanyl]glycine                  __________________________________________________________________________

EXAMPLES 36-55

Following the procedure of Example 1 but substituting for theglutathione in part (d) the peptide shown below in Col. I, one obtainsthe product shown in Col. II. ##STR14##

    __________________________________________________________________________    Example                                                                            A              A.sub.1                                                   __________________________________________________________________________    36                                                                                                NHCH.sub.2COOH                                            37                                                                                  ##STR15##     NHCH.sub.2COOH                                            38                                                                                  ##STR16##     NHCH.sub.2COOH                                            39                                                                                  ##STR17##     NHCH.sub.2COOH                                            40                                                                                  ##STR18##     NHCH.sub.2COOH                                            41                                                                                  ##STR19##     NHCH.sub.2COOH                                            42                                                                                  ##STR20##     NHCH.sub.2COOH                                            43                                                                                  ##STR21##     NHCH.sub.2COOH                                            44                                                                                  ##STR22##     NHCH.sub.2COOH                                            45                                                                                  ##STR23##     NHCH.sub.2COOH                                            46                                                                                  ##STR24##     NHCH.sub.2COOH                                            47                                                                                  ##STR25##     NHCH.sub.2COOH                                            48                                                                                  ##STR26##     NHCH.sub.2COOH                                            49                                                                                  ##STR27##                                                                                    ##STR28##                                                50                                                                                  ##STR29##                                                                                    ##STR30##                                                51                                                                                  ##STR31##                                                                                    ##STR32##                                                52                                                                                  ##STR33##                                                                                    ##STR34##                                                53                                                                                  ##STR35##                                                                                    ##STR36##                                                54                                                                                  ##STR37##                                                                                    ##STR38##                                                55                                                                                  ##STR39##                                                                                    ##STR40##                                                __________________________________________________________________________

Similarly, by employing the peptides of Col. I with the α-imino acidsshown in Col. I of Examples 2 to 35, other compounds within the scope ofthe invention are obtained.

EXAMPLE 56(S,S)-N-[3-[[3-(2-Carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine,trisodium salt

A solution of the product of Example 1 is treated with three equivalentsof sodium bicarbonate and lyophilized to give(S,S)-N-[3-[[3-(2-carboxy-1-pyrrolidinyl]-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine,trisodium salt.

In a similar manner, by employing potassium bicarbonate thecorresponding tripotassium salt is obtained.

EXAMPLE 57

1000 tablets each containing the following ingredients:

    ______________________________________                                        (S,S)-N-[3-[[3-(2-Carboxy-                                                    1-pyrrolidinyl)-2-methyl-3-                                                   oxopropyl]dithio]-N-(L-γ-glu-                                           tamyl)-L-alanyl]glycine,                                                      trisodium salt           100 mg.                                              Corn starch               50 mg.                                              Gelatin                   7.5 mg.                                             Avicel (microcrystalline                                                      cellulose)                25 mg.                                              Magnesium stearate        2.5 mg.                                                                      185 mg.                                              ______________________________________                                    

are prepared (from sufficient bulk quantities) by mixing the(S,S)-N-3-[[3-(2-carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]-glycine,trisodium salt and corn starch with an aqueous solution of the gelatin.The mixture is dried and ground to a fine powder. The Avicel and thenthe magnesium stearate are admixed with granulation. This mixture isthen compressed in a tablet press to form 1000 tablets each containing100 mg. of active ingredient.

EXAMPLE 58

An injectable solution is produced as follows:

    ______________________________________                                        (S,S)-N-[3-[[3-(2-Carboxy-1-                                                  pyrrolidinyl)-2-methyl-3-oxo-                                                 propyl]dithio]-N-(L-γ-glu-                                              tamyl)-L-alanyl]glycine 500     g.                                            Methyl paraben          5       g.                                            Propyl paraben          1       g.                                            Sodium chloride         25      g.                                            Water for injection qs. 5       l.                                            ______________________________________                                    

The active substance, preservatives and sodium chloride are dissolved in3 liters of water and then the volume is brought up to 5 liters. Thesolution is filtered through a sterile filter and asceptically filledinto presterilized vials which are then closed with presterilized rubberclosures. Each vial contains 5 ml. of solution in a concentration of 100mg. of active ingredient per ml. of solution for injection.

EXAMPLE 59

6000 tablets each containing the following ingredients:

    ______________________________________                                        (S,S)-N-[3-[[3-(2-Carboxy-1-                                                  pyrrolidinyl)-2-methyl-3-oxo-                                                 propyl]dithio]-N-(L-γ-glutamyl)-                                        L-alanyl]glycine         100 mg.                                              Avicel (microcrystalline                                                      cellulose)               100 mg.                                              Hydrochlorothiazide       12.5 mg.                                            Lactose U.S.P.           113 mg.                                              Corn starch U.S.P.        17.5 mg.                                            Stearic acid U.S.P.       7 mg.                                                                        350 mg.                                              ______________________________________                                    

are produced from sufficient bulk quantities by slugging the(S,S)-N-[3-[[3-(2-carboxy-1-pyrrolidinyl)-2-methyl-3-oxopropyl]dithio]-N-(L-γ-glutamyl)-L-alanyl]glycine,Avicel and a portion of the stearic acid. The slugs are ground andpassed through a #2 screen, and then the hydrochlorothiazide, lactose,corn starch and remainder of the stearic acid. The mixture is compressedinto 350 mg. capsule shaped tablets in a tablet press. The tablets arescored for dividing in half.

The products of Examples 2 to 55 can also be formulated according to theprocedure of Examples 57 to 59.

What is claimed is:
 1. A compound of the formula ##STR41## and saltsthereof, wherein A and A₁ are each amino acid residues independentlyselected from the group consisting of glycyl, alanyl, valyl, leucyl,α-glutamyl, γ-glutamyl, α-aspartyl, β-aspartyl, phenylalanyl, tyrosyl,tryptophyl, lysyl, arginyl and prolyl provided that at least one of Aand A₁ is tryptophyl, said A residue being joined through a carbonylgroup and said A₁ residue being joined through an amino group;R₁ ishydrogen, lower alkyl or halo substituted lower alkyl; X is an α-iminoacid residue selected from the group consisting of ##STR42## R₂ ishydrogen, hydroxy, lower alkyl, halogen, keto, ##STR43## Y is O or S; R₅is lower alkyl, phenyl, phenyl-lower alkylene, 1- or 2-naphthyl,biphenyl, substituted phenyl, substituted phenyl-lower alkylene,substituted 1- or 2-naphthyl, or substituted biphenyl wherein saidsubstituent is on the phenyl ring and is one or two members selectedfrom the group consisting of lower alkyl of 1 to 4 carbons, lower alkoxyof 1 to 4 carbons, lower alkylthio of 1 to 4 carbons, chloro, fluoro,trifluoromethyl, acetyloxy and hydroxy; R₆ is halogen or --Y--R₇ ; R₇ islower alkyl, phenyl, phenyl-lower alkylene, substituted phenyl, orsubstituted phenyl-lower alkylene wherein said substituent is one or twomembers selected from the group consisting of lower alkyl of 1 to 4carbons, lower alkoxy of 1 to 4 carbons, lower alkylthio of 1 to 4carbons, chloro, fluoro, trifluoromethyl, acetyloxy, and hydroxy, or theR₇ groups join in an alkylene chain of 2 or 3 carbons to complete a 5-or 6-membered ring or said ring in which one of the carbon atoms has alower alkyl or di(lower alkyl)substituent; and R₃ and R₄ areindependently selected from the group consisting of hydrogen and loweralkyl.
 2. The composition of claim 6 also including a diuretic.
 3. Themethod of alleviating hypertension which comprises administering aneffective amount of the composition of claim
 6. 4. A compound of claim 1whereinR₁ is hydrogen, methyl or trifluoromethyl; and X is (L)-proline,4-hydroxy-(L)-proline, 4-methoxy-(L)-proline,4,4-ethylenedioxo-(L)-proline, 4,4-ethylenedithio-(L)proline,4-phenoxy-(L)-proline, 4-phenylthio-(L)-proline,4-(2-naphthlenyloxy)-(L)-proline, or4-([1,1-biphenyl]-4-yloxy)-(L)proline.
 5. A compound of claim 4 whereinR₁ is methyl and X is (L)-proline.
 6. A composition for treatinghypertension comprising a pharmaceutically acceptable carrier and aneffective amount of one or more hypotensive agents or pharmaceuticallyacceptable salts thereof of the formula ##STR44## wherein A and A₁ areeach amino acid residues independently selected from the groupconsisting of glycyl, alanyl, valyl, leucyl, α-glutamyl, γ-glutamyl,α-aspartyl, β-aspartyl, phenylalanyl, tyrosyl, tryptophyl, lysyl,arginyl and prolyl provided that the least one of A and A₁ istryptophyl, said A residue being joined through a carbonyl group andsaid A₁ residue being joined through an amino group;R₁ is hydrogen,lower alkyl or halo substituted lower alkyl; X is an α-imino acidresidue selected from the group consisting of ##STR45## R₂ is hydrogen,hydroxy, lower alkyl, halogen, keto, ##STR46## Y is O or S; R₅ is loweralkyl, phenyl, phenyl-lower alkylene, 1- or 2-naphthyl, biphenyl,substituted phenyl, substituted phenyl-lower alkylene, substituted 1- or2-naphthyl, or substituted biphenyl wherein said substituent is on thephenyl ring and is one or two members selected from the group consistingof lower alkyl of 1 to 4 carbons, lower alkoxy of 1 to 4 carbons, loweralkylthio of 1 to 4 carbons, chloro, fluoro, trifluoromethyl, acetyloxy,and hydroxy; R₆ is halogen or --Y--R₇ ; R₇ is lower alkyl, phenyl,phenyl-lower alkylene, substituted phenyl, or substituted phenyl-loweralkylene wherein said substituent is one or two members selected fromthe group consisting of lower alkyl of 1 to 4 carbons, lower alkoxy of 1to 4 carbons, lower alkylthio of 1 to 4 carbons, chloro, fluoro,trifluoromethyl, acetyloxy, and hydroxy, or the R₇ groups join in analkylene chain of 2 or 3 carbons to complete a 5- or 6-membered ring orsaid ring in which one of the carbon atoms has a lower alkyl or di(loweralkyl)substituent; and R₃ and R₄ are independently selected from thegroup consisting of hydrogen and lower alkyl.